A digital subscriber line (DSL) network enables a user, through customer premise equipment (CPE) (e.g., modem, computer, set-top terminal, personal digital assistant, or other communication devices), to transmit data to, or receive data from, an upstream source via multiple data channels. DSL networks support a variety of different data, such as video, voice, voice over IP (VoIP), among other data. The customer premise equipment is typically located at a business or residence, and users at a terminal or endpoint, such as a computer or other electronic appliance, access the network through modems or a gateway.
FIG. 1 is a block diagram of an exemplary DSL network 100. The DSL network 100 includes a central office 102 that comprises a digital subscriber line access multiplexer (DSLAM) 103 that terminates a plurality of DSL lines from customer premise equipment at multiple locations 104, 106, and 108. Such locations 104, 106, and 108 may represent businesses or residences. Referring to location 104 as one exemplary arrangement, the CPE includes a television 110 coupled to a DSL modem 112, which is in bidirectional communication with the DSLAM 103 of the central office 102. The DSLAM 103 and the CPEs collectively comprise an access network 114. The central office 102 accesses a core network 115 comprising the Internet 116 and an ATM switch or router 118.
As is known, data interfaces, including Ethernet interfaces such as media independent interfaces (MII) or serial media independent interfaces (SMII), among others, are used in DSLAMs 103 to connect Ethernet physical layer transceivers or devices (such as a multi-port line card comprising a plurality of modems) to aggregation devices (e.g., such as a multi-port network processor or Ethernet switches). However, such Ethernet interfaces are not without shortcomings. For instance, line cards often have a plurality of ports (e.g., 24, 48, 72, 96) that have a corresponding SMII interface. One SMII interface per port translates to a larger number of SMII interfaces per line card, resulting in increased design complexity on the associated circuit board and an increased bill of material (BOM) for manufacturing purposes.
Further, such Ethernet interfaces have constraints with regards to bandwidth. For example, in a 100 Mbps interface, it is not possible to demonstrate a 100 Mbps throughput with 64-byte-sized packets since maximum SMII utilization at 64-byte packets is approximately 70% due to overhead (e.g., collectively, 12-byte interfame gap (IFG) and 8-byte preamble resulting in 20-byte or ˜30% overhead per 60-byte packet-payload). Additionally, each SMII link is limited to 100/100 Mbps traffic, whereas more advanced standards of DSL communications (e.g., very high speed digital subscriber line 2, or VDSL2) may have rates that increase beyond 100/100 Mbps. Also, there is a one-to-one connection or mapping between an SMII link and an xDSL line, preventing bandwidth sharing across SMII links.